Channel state information for adaptively configured TDD communication systems

ABSTRACT

For a base station or a User Equipment (UE) in communication with each other, the UE is configured by the base station for operation with an adapted Time Division Duplex (TDD) UpLink-DownLink (UL-DL) configuration. The base station configures a UE with resources for obtaining channel and interference measurements in two sets of Transmission Time Intervals (TTIs) and the UE obtains a Channel State Information (CSI) from the channel and interference measurements in the two sets of TTIs.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 14/201,087 Filed Mar. 7, 2014 and entitled “CHANNELSTATE INFORMATION FOR ADAPTIVELY CONFIGURED TDD COMMUNICATION SYSTEMS,”and claims priority through that application to U.S. Provisional PatentApplication Ser. No. 61/780,182 filed Mar. 13, 2013 and entitled“Channel State Information for Adaptively Configured TDD CommunicationSystems,” U.S. Provisional Patent Application Ser. No. 61/809,059 filedApr. 5, 2013 and entitled “Channel State Information for AdaptivelyConfigured TDD Communication Systems,” and U.S. Provisional PatentApplication Ser. No. 61/933,720 filed Jan. 30, 2014 and entitled“Channel State Information for Adaptively Configured TDD CommunicationSystems.” The above-identified patent documents are incorporated hereinby reference.

TECHNICAL FIELD

The present application relates generally to wireless communicationsand, more specifically, to providing channel state information forscheduling downlink and uplink transmissions in adaptively configuredtime division duplex (TDD) communication systems.

BACKGROUND

Wireless communication has been one of the most successful innovationsin modern history. Recently, the number of subscribers to wirelesscommunication services exceeded five billion and continues to growquickly. The demand of wireless data traffic is rapidly increasing dueto the growing popularity among consumers and businesses of smart phonesand other mobile data devices, such as tablets, “note pad” computers,net books, and eBook readers. In order to meet the high growth in mobiledata traffic, improvements in radio interface efficiency and allocationof new spectrum is of paramount importance.

SUMMARY

This disclosure provides a system and method for performing uplink anddownlink link adaptation in adaptively configured time division duplex(TDD) communication systems.

In a first embodiment, a method is provided. The method includestransmitting, by a base station to a User Equipment (UE), signalingindicating a first Time Division Duplexing (TDD) UpLink-DownLink (UL-DL)configuration. A TDD UL-DL configuration is defined over a time periodof ten SubFrames (SFs) that comprise DL SFs where a communicationdirection is from the base station to the UE, UL SFs where acommunication direction is from the UE to the base station, and specialSFs where a communication direction can be both from the base station tothe UE and from the UE to the base station. Each SF of the ten SFs has aunique time domain index. The method also includes transmitting, by thebase station to the UE, a control channel configured to convey a DLControl Information (DCI) format indicating an adaptation of the firstTDD UL-DL configuration to a second TDD UL-DL configuration, andconfiguration information for resources of a non-zero power ChannelState Information Reference Signal (CSI-RS), resources of a firstChannel State Information Interference Measurement (CSI-IM), andresources of a second CSI-IM wherein the non-zero power CSI-RSresources, the first CSI-IM resources and the second CSI-IM resourcesare respectively in a SF that is a DL SF, a DL SF, and an UL SF in thefirst TDD UL-DL configuration. In response to receiving, by the UE,signaling indicating the first TDD UL-DL configuration, the DCI formatindicating the second TDD UL-DL configuration, the configurationinformation, the UE measures a first quantity based on signalingreceived in the non-zero power CSI-RS resources and on the first CSI-IMresources and a second quantity based on signaling received in thenon-zero power CSI-RS resources and on the second CSI-IM resources whenthe UL SF is a DL SF in the second TDD UL-DL configuration.

In a second embodiment, a method is provided. The method includestransmitting, by a base station to a User Equipment (UE), signalingindicating a first Time Division Duplexing (TDD) UpLink-DownLink (UL-DL)configuration. A TDD UL-DL configuration is defined over a time periodof ten SubFrames (SFs) that comprise DL SFs where a communicationdirection is from the base station to the UE, UL SFs where acommunication direction is from the UE to the base station, and specialSFs where a communication direction can be both from the base station tothe UE and from the UE to the base station, and wherein each SF of theten SFs has a unique time domain index. The method also includestransmitting, by the base station to the UE, a control channel conveyinga DL Control Information (DCI) format indicating an adaptation of thefirst TDD UL-DL configuration to a second TDD UL-DL configuration. Inresponse to receiving, by the UE, the signaling indicating the first TDDUL-DL configuration and the DCI format indicating the second TDD UL-DLconfiguration, the UE measures a first quantity in a first set of DL SFsof the second TDD UL-DL configuration to determine a first Channel StateInformation (CSI) and a second quantity in a second set of DL SFs of thesecond TDD UL-DL configuration to determine a second CSI. In addition,the UE discards a measurement of the second quantity in a DL SF from thesecond set of DL SFs from the determination of the second CSI if themeasurement value is smaller than a second threshold value.

In a third embodiment, a base station is provided. The base stationincludes a transmitter configured to transmit, to a User Equipment (UE),signaling indicating a first Time Division Duplexing (TDD)UpLink-DownLink (UL-DL) configuration. A TDD UL-DL configuration isdefined over a time period of ten SubFrames (SFs) that comprise DL SFswhere a communication direction is from the base station to the UE, ULSFs where a communication direction is from the UE to the base station,and special SFs where a communication direction can be both from thebase station to the UE and from the UE to the base station, and whereineach SF of the ten SFs has a unique time domain index. The base stationalso includes a transmitter configured to transmit, to the UE, a controlchannel configured to convey a DL Control Information (DCI) formatindicating an adaptation of the first TDD UL-DL configuration to asecond TDD UL-DL configuration. The transmitter further is configured totransmit configuration information for resources of a non-zero powerChannel State Information Reference Signal (CSI-RS), resources of afirst Channel State Information Interference Measurement (CSI-IM), andresources of a second CSI-IM wherein the non-zero power CSI-RSresources. The first CSI-IM resources and the second CSI-IM resourcesare respectively in a SF that is a DL SF, a DL SF, and an UL SF in thefirst TDD UL-DL configuration.

In a fourth embodiment, a User Equipment (UE) is provided. The UEincludes a receiver configured to receive, from a base station,signaling indicating a first Time Division Duplexing (TDD)UpLink-DownLink (UL-DL) configuration. A TDD UL-DL configuration isdefined over a time period of ten SubFrames (SFs) that comprise DL SFswhere a communication direction is from a base station to the UE, UL SFswhere a communication direction is from the UE to the base station, andspecial SFs where a communication direction can be both from the basestation to the UE and from the UE to the base station. Each SF of theten SFs has a unique time domain index. The UE also includes a receiverconfigured to receive, from a base station, a control channeltransmitted from the base station and conveying a DL Control Information(DCI) format indicating an adaptation of the first TDD UL-DLconfiguration to a second TDD UL-DL configuration. The UE furtherincludes a measurement unit configured to measure a first quantity in afirst set of DL SFs of the second TDD UL-DL configuration to determine afirst Channel State Information (CSI) and a second quantity in a secondset of DL SFs of the second TDD UL-DL configuration to determine asecond CSI, wherein the measurement unit discards a measurement of thesecond quantity in a DL SF from the second set of DL SFs from thedetermination of the second CSI if the measurement value is smaller thana second threshold value.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware with one or more ofsoftware and/or firmware. The functionality associated with anyparticular controller may be centralized or distributed, whether locallyor remotely. The phrase “at least one of,” when used with a list ofitems, means that different combinations of one or more of the listeditems may be used, and only one item in the list may be needed. Forexample, “at least one of: A, B, and C” includes any of the followingcombinations: A, B, C, A and B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless communication network accordingto this disclosure;

FIG. 2 illustrates an example user equipment (UE) according to thisdisclosure;

FIG. 3 illustrates an example eNodeB (eNB) according to this disclosure;

FIG. 4 illustrates an example conventional PUSCH transmission structureover a Transmission Time Interval (TTI) according to this disclosure;

FIG. 5 illustrates an example transmitter block diagram for datainformation and UCI in a PUSCH according to this disclosure;

FIG. 6 illustrates an example receiver block diagram for datainformation and UCI in a PUSCH according to this disclosure;

FIG. 7 illustrates an example transmitter structure for a ZC sequencethat can be used as DMRS or as SRS according to this disclosure;

FIG. 8 illustrates an example presence or absence of UL controlsignaling or UL periodic signaling in an UL TTI according to thisdisclosure;

FIG. 9 illustrates an example adaptation of SRS BW configuration in ULflexible TTIs relative to UL fixed TTIs according to this disclosure;

FIG. 10 illustrates an example adaptation of SRS BW configuration in ULflexible TTIs when an UL BW is a fraction of an UL BW in UL fixed TTIsaccording to this disclosure;

FIG. 11 illustrates an example use of a first UE-specific higher layersignaling for P-SRS or A-SRS transmission parameters in UL fixed TTIsand of a second UE-specific higher layer signaling for P-SRS or A-SRStransmission parameters in UL flexible TTIs according to thisdisclosure;

FIG. 12 illustrates an example use of an UL TTI type A-SRS indicatorfield according to this disclosure;

FIG. 13 illustrates an example existence of different interferencecharacteristics in different flexible TTIs according to this disclosure;

FIG. 14 illustrates an example determination by an eNB of a DL CSI in afirst set of DL TTIs using a SRS transmission from a UE in a second setof UL TTIs according to this disclosure;

FIG. 15 illustrates an example eNB receiver for estimating a DL CSI in aTTI set based on a SRS transmission from a UE according to thisdisclosure; and

FIG. 16 illustrates an example for a UE to determine a first CSI from afirst set of DL TTIs or to determine a second CSI from a second set ofDL TTIs according to this disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 16, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged wireless communication system.

The following documents and standards descriptions are herebyincorporated into the present disclosure as if fully set forth herein:3GPP TS 36.211 v11.1.0, “E-UTRA, Physical channels and modulation” (REF1); 3GPP TS 36.212 v11.1.0, “E-UTRA, Multiplexing and Channel coding”(REF 2); 3 GPP TS 36.213 v11.1.0, “E-UTRA, Physical Layer Procedures”(REF 3); and 3GPP TS 36.331 v11.1.0, “E-UTRA, Radio Resource Control(RRC) Protocol Specification.” (REF 4).

This disclosure relates to the adaptation of communication direction inwireless communication networks that utilize Time Division Duplex (TDD).A wireless communication network includes a DownLink (DL) that conveyssignals from transmission points (such as base stations or eNodeBs) touser equipments (UEs). The wireless communication network also includesan UpLink (UL) that conveys signals from UEs to reception points such aseNodeBs.

FIG. 1 illustrates an example wireless network 100 according to thisdisclosure. The embodiment of the wireless network 100 shown in FIG. 1is for illustration only. Other embodiments of the wireless network 100could be used without departing from the scope of this disclosure.

As shown in FIG. 1, the wireless network 100 includes an eNodeB (eNB)101, an eNB 102, and an eNB 103. The eNB 101 communicates with the eNB102 and the eNB 103. The eNB 101 also communicates with at least oneInternet Protocol (IP) network 130, such as the Internet, a proprietaryIP network, or other data network.

Depending on the network type, other well-known terms may be usedinstead of “eNodeB” or “eNB,” such as “base station” or “access point.”For the sake of convenience, the terms “eNodeB” and “eNB” are used inthis patent document to refer to network infrastructure components thatprovide wireless access to remote terminals. Also, depending on thenetwork type, other well-known terms may be used instead of “userequipment” or “UE,” such as “mobile station,” “subscriber station,”“remote terminal,” “wireless terminal,” or “user device.” For the sakeof convenience, the terms “user equipment” and “UE” are used in thispatent document to refer to remote wireless equipment that wirelesslyaccesses an eNB, whether the UE is a mobile device (such as a mobiletelephone or smartphone) or is normally considered a stationary device(such as a desktop computer or vending machine).

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M) like a cell phone, a wireless laptop, a wireless PDA,or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, or other advanced wireless communication techniques.

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, various components of the network 100(such as the eNBs 101-103 and/or the UEs 111-116) support the adaptationof communication direction in the network 100, which can utilize TDD.

Although FIG. 1 illustrates one example of a wireless network 100,various changes may be made to FIG. 1. For example, the wireless network100 could include any number of eNBs and any number of UEs in anysuitable arrangement. Also, the eNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNB 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIG. 2 illustrates an example UE 114 according to this disclosure. Theembodiment of the UE 114 shown in FIG. 2 is for illustration only, andthe other UEs in FIG. 1 could have the same or similar configuration.However, UEs come in a wide variety of configurations, and FIG. 2 doesnot limit the scope of this disclosure to any particular implementationof a UE.

As shown in FIG. 2, the UE 114 includes an antenna 205, a radiofrequency (RF) transceiver 210, transmit (TX) processing circuitry 215,a microphone 220, and receive (RX) processing circuitry 225. The UE 114also includes a speaker 230, a main processor 240, an input/output (I/O)interface (IF) 245, a keypad 250, a display 255, and a memory 260. Thememory 260 includes a basic operating system (OS) program 261 and one ormore applications 262.

The RF transceiver 210 receives, from the antenna 205, an incoming RFsignal transmitted by an eNB or another UE. The RF transceiver 210down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 225, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 225 transmits the processed basebandsignal to the speaker 230 (such as for voice data) or to the mainprocessor 240 for further processing (such as for web browsing data).

The TX processing circuitry 215 receives analog or digital voice datafrom the microphone 220 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the main processor240. The TX processing circuitry 215 encodes, multiplexes, and/ordigitizes the outgoing baseband data to generate a processed baseband orIF signal. The RF transceiver 210 receives the outgoing processedbaseband or IF signal from the TX processing circuitry 215 andup-converts the baseband or IF signal to an RF signal that istransmitted via the antenna 205.

The main processor 240 can include one or more processors or otherprocessing devices and can execute the basic OS program 261 stored inthe memory 260 in order to control the overall operation of the UE 114.For example, the main processor 240 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceiver 210, the RX processing circuitry 225, and the TXprocessing circuitry 215 in accordance with well-known principles. Insome embodiments, the main processor 240 includes at least onemicroprocessor or microcontroller.

The main processor 240 is also capable of executing other processes andprograms resident in the memory 260 such as operations in support ofproviding channel state information for scheduling downlink and uplinktransmissions in adaptively configured time division duplex (TDD)communication systems. The main processor 240 can move data into or outof the memory 260 as required by an executing process. In someembodiments, the main processor 240 is configured to execute theapplications 262 based on the OS program 261 or in response to signalsreceived from eNBs, other UEs, or an operator. The main processor 240 isalso coupled to the I/O interface 245, which provides the UE 114 withthe ability to connect to other devices such as laptop computers andhandheld computers. The I/O interface 245 is the communication pathbetween these accessories and the main processor 240.

The main processor 240 is also coupled to the keypad 250 and the displayunit 255. The operator of the UE 114 can use the keypad 250 to enterdata into the UE 114. The display 255 may be a liquid crystal display orother display capable of rendering text and/or at least limitedgraphics, such as from web sites. The display 255 could also represent atouchscreen.

The memory 260 is coupled to the main processor 240. Part of the memory260 could include a random access memory (RAM), and another part of thememory 260 could include a Flash memory or other read-only memory (ROM).

As described in more detail below, the transmit and receive paths of theUE 114 (implemented using the RF transceiver 210, TX processingcircuitry 215, and/or RX processing circuitry 225) support downlinksignaling for uplink and downlink adaptation in adaptively configuredTDD systems.

Although FIG. 2 illustrates one example of UE 114, various changes maybe made to FIG. 2. For example, various components in FIG. 2 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, themain processor 240 could be divided into multiple processors, such asone or more central processing units (CPUs) and one or more graphicsprocessing units (GPUs). Also, while FIG. 2 illustrates the UE 114configured as a mobile telephone or smartphone, UEs could be configuredto operate as other types of mobile or stationary devices. In addition,various components in FIG. 2 could be replicated, such as when differentRF components are used to communicate with the eNBs 101-103 and withother UEs.

FIG. 3 illustrates an example eNB 102 according to this disclosure. Theembodiment of the eNB 102 shown in FIG. 3 is for illustration only, andother eNBs of FIG. 1 could have the same or similar configuration.However, eNBs come in a wide variety of configurations, and FIG. 3 doesnot limit the scope of this disclosure to any particular implementationof an eNB.

As shown in FIG. 3, the eNB 102 includes multiple antennas 305 a-305 n,multiple RF transceivers 310 a-310 n, transmit (TX) processing circuitry315, and receive (RX) processing circuitry 320. The eNB 102 alsoincludes a controller/processor 325, a memory 330, and a backhaul ornetwork interface 335.

The RF transceivers 310 a-310 n receive, from the antennas 305 a-305 n,incoming RF signals, such as signals transmitted by UEs or other eNBs.The RF transceivers 310 a-310 n down-convert the incoming RF signals togenerate IF or baseband signals. The IF or baseband signals are sent tothe RX processing circuitry 320, which generates processed basebandsignals by filtering, decoding, and/or digitizing the baseband or IFsignals. The RX processing circuitry 320 transmits the processedbaseband signals to the controller/ processor 325 for furtherprocessing.

The TX processing circuitry 315 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 325. The TX processing circuitry 315 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 310 a-310 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 315 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 305 a-305 n.

The controller/processor 325 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 325 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 310 a-310 n, the RX processing circuitry 320, andthe TX processing circuitry 315 in accordance with well-knownprinciples. The controller/processor 325 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 325 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 305 a-305 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 325. In some embodiments, the controller/processor325 includes at least one microprocessor or microcontroller.

The controller/processor 325 is also capable of executing programs andother processes resident in the memory 330, such as a basic OS. Thecontroller/processor 325 can move data into or out of the memory 330 asrequired by an executing process.

The controller/processor 325 is also coupled to the backhaul or networkinterface 335. The backhaul or network interface 335 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 335 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 335 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 335 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 335 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 330 is coupled to the controller/processor 325. Part of thememory 330 could include a RAM, and another part of the memory 330 couldinclude a Flash memory or other ROM.

As described in more detail below, the transmit and receive paths of theeNB 102 (implemented using the RF transceivers 310 a-310 n, TXprocessing circuitry 315, and/or RX processing circuitry 320) supportdownlink signaling for uplink and downlink adaptation in adaptivelyconfigured TDD systems.

Although FIG. 3 illustrates one example of an eNB 102, various changesmay be made to FIG. 3. For example, the eNB 102 could include any numberof each component shown in FIG. 3. As a particular example, an accesspoint could include a number of interfaces 335, and thecontroller/processor 325 could support routing functions to route databetween different network addresses. As another particular example,while shown as including a single instance of TX processing circuitry315 and a single instance of RX processing circuitry 320, the eNB 102could include multiple instances of each (such as one per RFtransceiver).

In some wireless networks, DL signals include data signals conveyinginformation content, control signals conveying DL Control Information(DCI), and Reference Signals (RS), which are also known as pilotsignals. An eNB can transmit data information or DCI through respectivePhysical DL Shared CHannels (PDSCHs) or Physical DL Control CHannels(PDCCHs). Enhanced PDCCHs (EPDCCHs) can also be used but for brevityfurther reference to EPDCCHs is omitted.

An eNB, such as eNB 102, can transmit one or more of multiple types ofRS, including a UE-Common RS (CRS), a Channel State Information RS(CSI-RS), and a DeModulation RS (DMRS). A CRS can be transmitted over aDL system BandWidth (BW) and can be used by UEs, such as UE 114, todemodulate data or control signals or to perform measurements. To reduceCRS overhead, eNB 102 can transmit a CSI-RS with a smaller density inthe time or frequency domain than a CRS. For channel measurement,Non-Zero Power CSI-RS (NZP CSI-RS) resources can be used. Forinterference measurement, UE 114 can use CSI Interference Measurement(CSI-IM) resources associated with a Zero Power CSI-RS (ZP CSI-RS) thatis configured to UE 114 by a serving eNB 102 using higher layersignaling. A NZP CSI-RS configuration can include a number of CSI-RSantenna ports, a resource configuration, a time configuration, and so on(see also REF 3). A CSI-IM resource configuration can include a ZPCSI-RS configuration (pattern) and a ZP CSI-RS subframe configuration(see also REF 1 and REF 3). UE 114 is not expected to receive CSI-IMresource configurations that are not all completely overlapping with oneZP CSI-RS resource configuration. A CSI process consists of one NZPCSI-RS and one CSI-IM. UE 114 can use either a CRS or a CSI-RS toperform measurements and a selection can be based on a Transmission Mode(TM) that UE 114 is configured for PDSCH reception (see also REF 3).Finally, DMRS is transmitted only in the BW of a respective PDSCH orPDCCH, and UE 114 can use the DMRS to demodulate information in a PDSCHor PDCCH.

In some wireless networks, UL signals can include data signals conveyinginformation content, control signals conveying UL Control Information(UCI), and RS. UE 114 can transmit data information or UCI through arespective Physical UL Shared CHannel (PUSCH) or a Physical UL ControlCHannel (PUCCH). If UE 114 simultaneously transmits data information andUCI, UE 114 can multiplex both in a PUSCH. The UCI can include HybridAutomatic Repeat reQuest ACKnowledgement (HARQ-ACK) informationindicating correct or incorrect detection of data Transport Blocks (TBs)in a PDSCH, Service Request (SR) information indicating whether UE 116has data in its buffer, and Channel State Information (CSI) enabling eNB102 to select appropriate parameters for PDSCH transmissions to UE 114.HARQ-ACK information can include a positive ACKnowledgement (ACK) inresponse to a correct PDCCH or data TB detection, a NegativeACKnowledgement (NACK) in response to an incorrect data TB detection,and an absence of a PDCCH detection (DTX) that can be implicit orexplicit. A DTX could be implicit if UE 114 does not transmit a HARQ-ACKsignal. A DTX can be explicit if UE 114 can identify missed PDCCHs inother ways (it is also possible to represent NACK and DTX with the sameNACK/DTX state).

The CSI can include a Channel Quality Indicator (CQI) informing eNB 102of Transport Block Size (TBS) that can be received by the UE with apredefined target BLock Error Rate (BLER), a Precoding Matrix Indicator(PMI) informing eNB 102 how to combine signals from multiple transmittedantennas in accordance with a Multiple Input Multiple Output (MIMO)transmission principle, and a Rank Indicator (RI) indicating atransmission rank for a PDSCH. For example, UE 114 can determine a CQIfrom a Signal-to-Noise and Interference (SINR) measurement while alsoconsidering a configured PDSCH TM and the UE's receiver characteristics.Therefore, a CQI report from UE 114 can provide a serving eNB 102 anestimate of the SINR conditions experienced by DL signal transmissionsto UE 114.

CSI transmission from UE 114 can be periodic (P-CSI) or aperiodic(A-CSI) as triggered by a CSI request field included in a DCI formatconveyed by a PDCCH scheduling PUSCH. The UL RS can include DMRS andSounding RS (SRS). DMRS can be transmitted only in a BW of a respectivePUSCH or PUCCH, and eNB 102 can use a DMRS to demodulate information ina PUSCH or PUCCH. SRS can be transmitted by UE 114 in order to provideeNB 102 with a UL CSI. SRS transmission from UE 114 can be periodic(P-SRS or type 0 SRS) at predetermined Transmission Time Intervals(TTIs) with transmission parameters configured to UE 114 by higher-layersignaling, such as Radio Resource Control (RRC) signaling (see also REF4). SRS transmission from UE 114 can also be aperiodic (A-SRS, or type 1SRS) as triggered by a SRS request field included in a DCI formatconveyed by a PDCCH scheduling PUSCH or PDSCH and indicating A-SRStransmission parameters from a set of A-SRS transmission parameters thatwere previously configured to UE 114 by a serving eNB 102 (see also REF2 and REF 3).

When UE 114 is configured simultaneous transmission of P-CSI and A-CSIor of P-SRS and A-SRS for a same cell, it prioritizes a transmission forthe A-CSI and the A-SRS, respectively, and suspends a transmission forthe P-CSI and the P-SRS. In case UE 114 is configured with multiple CSIprocesses and needs to simultaneously transmit more than one P-CSIcorresponding to different CSI processes, it prioritizes the P-CSItransmission associated with the smaller CSI process index and suspendsother P-CSI transmissions. In case UE 114 is configured to reportmultiple P-CSI corresponding to respective multiple DL cells orconfigured to transmit multiple P-SRS corresponding to respectivemultiple DL cells and needs to simultaneously transmit more than oneP-CSI or more than one P-SRS, respectively, it prioritizes the P-CSItransmission associated with the smaller DL cell index or the P-SRStransmission associated with the smaller UL cell index and suspendsother P-CSI transmissions or P-SRS transmissions, respectively (see alsoREF 3).

FIG. 4 illustrates an example PUSCH transmission structure over a TTIaccording to this disclosure. The embodiment of the PUSCH transmissionstructure 400 over a TTI shown in FIG. 4 is for illustration only. Otherembodiments could be used without departing from the scope of thepresent disclosure.

As shown in FIG. 4, a TTI is one subframe 410 that includes two slots.Each slot 420 includes N_(symb) ^(UL) symbols 430 for transmitting datainformation, UCI, or RS. Some PUSCH symbols in each slot are used fortransmitting DMRS 440. A transmission BW includes frequency resourceunits that are referred to as Resource Blocks (RBs). Each RB includesN_(sc) ^(RB) sub-carriers, or Resource Elements (REs), and UE 114 isallocated M_(PUSCH) RBs 450 for a total of M_(sc)^(PUSCH)=M_(PUSCH)·N_(sc) ^(RB) REs for a PUSCH transmission BW. Thelast TTI symbol may be used to multiplex SRS transmissions 460 from oneor more UEs. A number of TTI symbols available for data/UCI/DMRStransmission is N_(symb) ^(PUSCH)=2·(N_(symb) ^(UL)−1)−N_(SRS), whereN_(SRS)=1 if a last TTI symbol is used to transmit SRS and N_(SRS)=0otherwise.

FIG. 5 illustrates an example transmitter block diagram for datainformation and UCI in a PUSCH according to this disclosure. Theembodiment of the transmitter 500 shown in FIG. 5 is for illustrationonly. Other embodiments could be used without departing from the scopeof the present disclosure. In certain embodiments, transmitter 500 islocated within eNB 102. In certain embodiments, transmitter 500 islocated within UE 114.

As shown in FIG. 5, coded CSI symbols 505 and coded data symbols 510 aremultiplexed by multiplexer 520. Coded HARQ-ACK symbols are then insertedby multiplexer 530 by puncturing data symbols and/or CSI symbols. Atransmission of coded RI symbols is similar to one for coded HARQ-ACKsymbols (not shown). The Discrete Fourier Transform (DFT) is obtained byDFT unit 540, REs 550 corresponding to a PUSCH transmission BW areselected by selector 555, an Inverse Fast Fourier Transform (IFFT) isperformed by IFFT unit 560, an output is filtered and by filter 570 andapplied a certain power by Power Amplifier (PA) 580 and a signal is thentransmitted 590. Additional transmitter circuitry such asdigital-to-analog converter, filters, amplifiers, and transmitterantennas as well as encoders and modulators for data symbols and UCIsymbols are omitted for brevity.

FIG. 6 illustrates an example receiver block diagram for datainformation and UCI in a PUSCH according to this disclosure. Theembodiment of the receiver 600 shown in FIG. 6 is for illustration only.Other embodiments could be used without departing from the scope of thepresent disclosure. In certain embodiments, receiver 600 is locatedwithin eNB 102 In certain embodiments, receiver 600 is located within UE114.

As shown in FIG. 6, a received signal 610 is filtered by filter 620, aFast Fourier Transform (FFT) is applied by FFT unit 630, a selector unit640 selects REs 650 used by a transmitter, an Inverse DFT (IDFT) unitapplies an IDFT 660, a de-multiplexer 670 extracts coded HARQ-ACKsymbols and places erasures in corresponding REs for data symbols andCSI symbols and finally another de-multiplexer 680 separates coded datasymbols 690 and coded CSI symbols 695. A reception of coded RI symbolsis similar to one for coded HARQ-ACK symbols (not shown). Additionalreceiver circuitry such as a channel estimator, demodulators anddecoders for data and UCI symbols are not shown for brevity.

A DMRS or SRS transmission can be through a transmission of a respectiveZadoff-Chu (ZC) sequence (see also REF 1). For an UL system BW of N_(RB)^(max,UL) RBs, a sequence r_(u,v) ^((α))(n) can be defined by a CyclicShift (CS) α of a base sequence r _(u,v)(n) according to r_(u,v)^((α))(n)=e^(jan) r _(u,v)(n), 0≤n≤M_(sc) ^(RS)=mN_(sc) ^(RB) is asequence length, 1≤m≤N_(RB) ^(max,UL), and r _(u,v)(n)=x_(q)(n modN_(ZC) ^(RS)) where the qth root ZC sequence is defined by

${{x_{q}(m)} = {\exp\left( \frac{{- j}\;\pi\;{m\left( {m + 1} \right)}}{N_{ZC}^{RS}} \right)}},$0≤m≤N_(ZC) ^(RS)−1 with q given by q=└q+½┘+v·(−1)^(└2q┘) and q given byq=N_(ZC) ^(RS)·(u+1)/31. A length N_(ZC) ^(RS) of a ZC sequence is givenby a largest prime number such that N_(ZC) ^(RS)<M_(sc) ^(RS). MultipleRS sequences can be defined from a single base sequence using differentvalues of α.

FIG. 7 illustrates an example transmitter structure for a ZC sequencethat can be used as DMRS or as SRS according to this disclosure. Theembodiment of the transmitter 700 shown in FIG. 7 is for illustrationonly. Other embodiments could be used without departing from the scopeof the present disclosure. In certain embodiments, transmitter 700 islocated within eNB 102.

As shown in FIG. 7, a mapper 720 maps a ZC sequence of length M_(sc)^(RS) 710 to REs of a transmission BW as they are indicated by REselection unit 730. The mapping can be to consecutive REs for a DMRS orto alternate REs for a SRS thereby creating a comb spectrum.Subsequently, an IFFT is performed by IFFT unit 740, a CS is applied tothe output by CS unit 750, and a resulting signal is filtered by filter760. Finally, a transmission power is applied by power amplifier 770 andthe RS is transmitted 780.

TABLE 1 lists a number of combinations for a SRS transmission BW. eNB102 can signal a SRS BW configuration c through a broadcast channel, forexample 3 bits can indicate one of the eight configurations in TABLE 1.eNB 102 can then assign to each UE, such as UE 114, UE 115, UE 116 a SRStransmission BWs m_(SRS,b) ^(c) (in RBs) by indicating the value of bfor SRS BW configuration c. For P-SRS, this can be by higher layersignaling of 2 bits. For A-SRS, this can be by a respective DCI formatdynamically indicating one BW from a set of BWs configured to a UE byhigher layer signaling. A variation in a maximum SRS BW is primarilyintended to accommodate a varying total PUCCH size. PUCCHs are assumedto be transmitted at the two edges of an UL BW and may not be overlappedwith SRS. Therefore, the larger a total PUCCH size (in RBs), the smallera maximum SRS transmission BW. That is, as a total PUCCH size (in RBs)increases, the maximum SRS transmission BW decreases.

TABLE 1 m_(SRS, b) ^(c) RB values for UL BW of N_(RB) ^(UL) RBs with 80< N_(RB) ^(UL) ≤ 110. SRS BW configuration b = 0 b = 1 b = 2 b = 3 c = 096 48 24 4 c = 1 96 32 16 4 c = 2 80 40 20 4 c = 3 72 24 12 4 c = 4 6432 16 4 c = 5 60 20 Not 4 Applicable c = 6 48 24 12 4 c = 7 48 16 8 4

In a TDD communication system, a communication direction in some TTIs isin the DL, and a communication direction in some other TTIs is in theUL. TABLE 2 lists indicative UL-DL configurations over a period of 10TTIs (a TTI has a duration of 1 millisecond (msec)), which is alsoreferred to as frame period. “D” denotes a DL TTI, “U” denotes a UL TTI,and “S” denotes a special TTI that includes a DL transmission fieldreferred to as DwPTS, a Guard Period (GP), and a UL transmission fieldreferred to as UpPTS. Several combinations exist for a duration of eachfield in a special TTI subject to the condition that the total durationis one TTI.

TABLE 2 TDD UL-DL configurations TDD UL-DL DL-to-UL Configu-Switch-point TTI number ration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms DS U U U D S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D3 10 ms  D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S UD D D D D D D 6 5 ms D S U U U D S U U D

The TDD UL-DL configurations in TABLE 2 provide 40% and 90% of DL TTIsper frame to be DL TTIs (and the remaining to be UL TTIs). Despite thisflexibility, a semi-static TDD UL-DL configuration that can be updatedevery 640 msec or less frequently, by signaling of a System InformationBlock (SIB) or, in case of DL Carrier Aggregation and secondary cell, byRRC signaling (see also REF 3 and REF 4), may not match well withshort-term data traffic conditions. For the remaining of thisdisclosure, such a TDD UL-DL configuration will be referred to as aconventional (or non-adapted) TDD UL-DL configuration and it is assumedto be used by conventional (or legacy) UEs in a cell. For this reason, afaster adaptation period of a TDD UL-DL configuration can improve systemthroughput, particularly for a low or moderate number of connected UEs.For example, when there is more DL traffic than UL traffic, aconventional TDD UL-DL configurations can be adapted every 10, 20, 40,or 80 msec to a different TDD UL-DL configuration that includes more DLTTIs. Signaling for faster adaptation of a TDD UL-DL configuration canbe provided by several mechanisms, including signaling a DCI format in aPDCCH.

An operating constraint in an adaptation of a conventional TDD UL-DLconfiguration, in ways other than conventional ones, is the possibleexistence of UEs that cannot be aware of such adaptation. Such UEs arereferred to as conventional UEs. Since conventional UEs performmeasurements in DL TTIs using a respective CRS, such DL TTIs cannot bechanged to UL TTIs or to special TTIs by a faster adaptation of theconventional TDD UL-DL configuration. However, an UL TTI can be changedto a DL TTI without impacting conventional UEs because eNB 102 canensure that such UEs do not transmit any signals in such UL TTIs. Inaddition, an UL TTI common to all TDD UL-DL configurations could existto enable eNB 102 to possibly select this UL TTI as the only UL one. Insome implementations, including all TDD-UL-DL configurations in TABLE 2,this UL TTI is TTI#2.

A TTI is referred to as DL flexible TTI if it is an UL TTI in aconventional TDD UL-DL configuration and is adapted to a DL TTI in anadapted TDD UL-DL configuration. A TTI is referred to as UL flexible TTIif it is an UL TTI in a conventional TDD UL-DL configuration that couldbe adapted to a DL TTI in an adapted TDD UL-DL configuration but itremains an UL TTI. Considering the above, TABLE 3 indicates flexibleTTIs (denoted by ‘F’) for each TDD UL-DL configuration in TABLE 2.Evidently, as DL TTIs in a conventional TDD UL-DL configuration cannotbe changed to UL TTIs, not all TDD UL-DL configurations can be used foradaptation. For example, if TDD UL-DL configuration 2 is theconventional one, an adaptation can be only to TDD UL-DL configuration5. Also, a use of a configured TDD UL-DL configuration for a UE toderive UL TTIs for HARQ-ACK transmissions further restricts TDD UL-DLconfiguration that can be used for adaptation as such UL TTIs are thenUL fixed TTIs. Therefore, an indication for an adaptation for a TDDUL-DL configuration can be considered by UE 114 as invalid if, forexample, UE 114 adapts a DL TTI in the conventional TDD UL-DLconfiguration in an UL TTI. Invalid indications can be caused, byexample, by the misdetection from UE 114 of a DCI format conveying anindication for an adapted TDD UL-DL configuration.

TABLE 3 Flexible TTIs (F) for TDD UL-DL configurations TDD UL-DLDL-to-UL Configu- Switch-point TTI number ration periodicity 0 1 2 3 4 56 7 8 9 0 5 ms D S U F F D F F F F 1 5 ms D S U F D D F F F D 2 5 ms D SU D D D F F D D 3 10 ms  D S U F F D D D D D 4 10 ms  D S U F D D D D DD 5 10 ms  D S U D D D D D D D 6 5 ms D S U F F D F F F D

If an eNB can adapt a TDD UL-DL configuration more frequently than byRRC signaling, for example using physical layer signaling, then flexibleTTIs (which can be only UL TTIs in the conventional TDD UL-DLconfiguration) should not carry any periodic UL signaling fromconventional UEs as this is configured by RRC signaling. This impliesthat in flexible TTIs conventional UEs should not be configuredtransmissions of SRS, or CSI, or SR, or HARQ-ACK signaling in responseto SPS PDSCH. Additionally, if a reference TDD UL-DL configuration isused for HARQ-ACK signaling in response to PDSCH receptions, arespective UL TTI should not be adapted to a DL TTI and, therefore, itis not a flexible TTI. However, there is a need for a UE to transmit SRSin UL flexible TTIs since, as it is further subsequently discussed, theinterference experienced by a signal transmission from the UE can bedifferent than in UL fixed TTIs and an eNB needs to obtain a respectiveUL CSI for the UE in a flexible TTI.

FIG. 8 illustrates an example presence or absence of UL controlsignaling or UL periodic signaling in an UL TTI according to thisdisclosure. The embodiment of the signaling shown in FIG. 8 is forillustration only. Other embodiments could be used without departingfrom the scope of the present disclosure.

As shown in FIG. 8, assuming TDD UL-DL configuration 1 is a conventionalTDD UL-DL configuration 810, TTI#2 820 is of UL fixed direction whileTTI#3 830, TTI#7 840, and TTI#8 850 are of flexible direction. As it ispossible for these flexible TTIs to be configured as DL TTIs at a ratefaster than an RRC configuration rate, they may not be configured withperiodic signaling, such as periodic CSI, SR, periodic SRS, and SPSPUSCH, from conventional UEs. Moreover, for simplifying a timeline forHARQ-ACK transmissions in response to scheduled PDSCH receptions, theseflexible TTIs may also not be used for dynamic HARQ-ACK transmissions.Then, all these aforementioned UL transmissions need to occur in the ULfixed TTI.

To extend a transmission bandwidth for UE 114 and support higher datarates, Carrier Aggregation (CA) can be used, where multiple componentcarriers (or cells) are aggregated and jointly used for transmission tothe UE (DL CA) or from the UE (UL CA). In some implementations, up tofive component carriers can be aggregated for UE 114. The number ofcomponent carriers used for DL CA can be different than the number ofcomponent carriers used for UL CA. Before CA is configured, UE 114 mayhave only one RRC connection with a network. One serving cell providesthe mobility information at RRC connectionestablishment/re-establishment/handover, and one serving cell providesthe security input at RRC connection re-establishment/handover. Thiscell is referred to as the Primary Cell (PCell). A DL carriercorresponding to the PCe 11 is referred to as a DL Primary ComponentCarrier (DL PCC), and its associated UL carrier is referred to as a ULPrimary Component Carrier (UL PCC). Depending on UE capabilities, DL orUL Secondary Cells (SCells) can be configured to form (together with thePCe 11) a set of serving cells. A carrier corresponding to an SCell isreferred to as a DL Secondary Component Carrier (DL SCC) in the DL,while it is referred to as a UL Secondary Component Carrier (UL SCC) inthe UL. The PCell and the SCells configured for UE 114 may not have thesame TDD UL-DL configuration or reconfiguration. In case an eNB supportsCA and adaptation of TDD UL-DL configurations, a DCI format indicatingadapted TDD UL-DL configurations can include respective three-bitindicators for multiple cells.

Embodiments of this disclosure provide a mechanism for supportingperiodic SRS transmissions in an UL flexible TTI that, in addition, canbe substantially over a bandwidth available for PUSCH transmissions.Embodiments of this disclosure also provide a mechanism for supportingaperiodic SRS transmissions in an UL flexible TTI that, in addition, canbe substantially over a bandwidth available for PUSCH transmissions.Embodiments of this disclosure also provide a mechanism for a UE todetermine if an aperiodic SRS transmission is for an UL fixed TTI or foran UL flexible TTI. Embodiments of this disclosure also provide amechanism for supporting periodic CSI transmissions for a DL flexibleTTI in a PUCCH. Embodiments of this disclosure provide a mechanism forsupporting aperiodic CSI transmissions for a DL flexible TTI in a PUSCH.Embodiments of this disclosure also provide a mechanism for UE 114 todetermine if an aperiodic CSI transmission is for a DL fixed TTI or fora DL flexible TTI. Moreover, embodiments of this disclosure provide amechanism for eNB 102 to perform DL link adaptation for UE 114 in a DLfixed TTI or in a DL flexible TTI based, respectively, on a reception ofa SRS that is transmitted from UE 114 in an UL flexible TTI or in an ULfixed TTI. Furthermore, embodiments of this disclosure provide amechanism for UE 114 to measure CSI for a first set of TTIs thatincludes DL fixed TTIs and for a second set of TTIs that includes DLflexible TTIs.

Support of a P-SRS Transmissions in an UL Flexible TTI

In certain embodiments, upon an adaptation of a TDD UL-DL configuration,it is desirable for eNB 102 to obtain as early as possible an UL CSI foran UL flexible TTI from UE 114 in order to determine an interferenceexperienced by UE 114, which can be different than an interferenceexperienced in an UL fixed TTI, and perform link adaptation forrespective PUSCH transmissions in UL flexible TTIs before a nextadaptation of a TDD UL-DL configuration in its own cell or in adifferent cell as this would again change the interferencecharacteristics. Triggering A-SRS transmission from UE 114 can achievethis objective for some UEs but cannot be a general solution due toassociated PDCCH resource requirements for scheduling PUSCHtransmissions in UL flexible TTIs, preferably as soon as possible aftera TDD UL-DL configuration adaptation, and as not all UEs may requiresuch PUSCH transmissions.

To avoid relying on an availability of PDCCH resources or on anexistence of data to transmit in PUSCHs by respective UEs in UL flexibleTTIs after a TDD UL-DL configuration adaptation, embodiments of thepresent disclosure consider that P-SRS transmissions in an UL flexibleTTI are configured to UE 114 separately from P-SRS transmissions in anUL fixed TTI. P-SRS transmissions in an UL flexible TTI occur only whenUE 114 knows that the communication direction in that TTI is in the UL(as determined by signaling, such as a DCI format transmitted in a PDCCHindicating an adapted TDD UL-DL configuration); otherwise, if thecommunication direction in a flexible TTI is in the DL or if UE 114 doesnot know the actual communication direction (DL or UL) in a flexibleTTI, due to an inability to receive the previous signaling, UE 114 doesnot transmit P-SRS. The UL flexible TTI with the P-SRS transmission canbe, for example, the first UL flexible TTI in an adapted TDD UL-DLconfiguration, or can be a first UL flexible TTI in a set of configuredTTIs to UE 114. P-SRS transmissions in an UL fixed TTI always occur witha configured periodicity until reconfigured by higher layer signalingfrom eNB 102. Moreover, as it is subsequently discussed, as some UEs mayexperience different interference in respective different UL flexibleTTIs, P-SRS transmissions may be configured in multiple UL flexible TTIsin a same frame. Nevertheless, it is also possible for a P-SRStransmission to be triggered only by the DCI format in the respectivePDCCH. Then, P-SRS is similar to A-SRS but instead of a singletransmission, a transmission can be periodic as long as the flexible TTIis an UL flexible TTI.

As P-SRS transmission parameters are both UE-common (informed to UEs bySIB signaling) and UE-specific (informed to UEs by UE-specific higherlayer signaling such as RRC signaling), UE-common P-SRS transmissionparameters in an UL flexible TTI can be implicitly derived fromrespective ones in an UL fixed TTI while UE-specific P-SRS transmissionparameters in UL flexible TTIs can be informed by separate higher layersignaling than in UL fixed TTIs. UE 114 can be informed that eNB 102applies TDD UL-DL configuration adaptation either by reserved fields ina SIB, that cannot be interpreted by conventional UEs, or by higherlayer signaling after UE 102 connects to eNB 102 as conventional UE.

UE-common P-SRS parameters for a UL fixed TTI include:

-   -   a) P-SRS BW configuration.    -   b) P-SRS transmission TTIs (starting TTI and periodicity of TTIs        where P-SRS can be transmitted; for example, the starting TTI        can be TTI#2 and P-SRS transmission TTIs can occur every 5 TTIs        or every 10 TTIs).    -   c) Whether a UE multiplexes a P-SRS transmission and a HARQ-ACK        signal transmission in a PUCCH or drops P-SRS transmission when        it transmits a HARQ-ACK signal in a PUCCH.    -   d) Number of UpPTS symbols for transmitting P-SRS, if applicable        (can be either one or two).

In a first approach for a SRS BW configuration, since UL flexible TTIsare considered to not contain PUCCH or SPS PUSCH transmissions fromconventional UEs and also not contain such transmissions from UEssupporting TDD UL-DL configuration adaptations on a faster time scale,all UL BW in UL flexible TTIs can become available for PUSCHtransmissions. Therefore, a P-SRS transmission can extend over all UL BWin order to provide a respective UL CSI. Moreover, due to the duality ofa UL/DL channel in TDD operation, information provided by SRS may alsobe used, at least partially, for link adaptation of PDSCH transmissions(possibly together with additional information as it is furthersubsequently discussed). Then, for example, P-SRS transmission BWconfiguration c=0 as listed in TABLE 1 (or another P-SRS BWconfiguration with maximum BW equal to or larger than the one used forP-SRS transmissions in UL fixed TTIs) can be used for SRS transmissionsin UL flexible TTIs regardless of the P-SRS transmission BWconfiguration signaled by a SIB for UL fixed TTIs. Therefore, the SRS BWconfiguration in UL flexible TTIs can be separately informed to UE 114by including it in a higher layer signaling or can be specified in asystem operation.

FIG. 9 illustrates an example adaptation of SRS BW configuration in anUL flexible TTI relative to an UL fixed TTI according to thisdisclosure. The embodiment of the SRS BW configuration shown in FIG. 9is for illustration only. Other embodiments could be used withoutdeparting from the scope of the present disclosure.

As shown in FIG. 9, in an UL fixed TTI, a SIB informs of SRS BWconfiguration c=3 900. PUCCH RBs are located at the two UL BW edges 902and 904. As SRS transmission in PUCCH RBs is not beneficial for linkadaptation and as simultaneous transmission in a same RB of SRS andPUCCH may not be universally supported for all PUCCH types, SRStransmission is typically constrained in RBs that can be used for PUSCHtransmission. Therefore, the larger the PUCCH size (in RBs), the smallerthe maximum SRS transmission BW should be and the SRS BW configurationsin TABLE 1 support such functionality. UE 114 is configured by higherlayer signaling a P-SRS transmission BW with either m_(SRS,0) ³=72 RBs912, or m_(SRS,1) ³=24 RBs 914, or m_(SRS,2) ³=12 RBs 916, or m_(SRS,3)³=4 RBs 918. A few RBs, 906 and 908, may not be sounded but this usuallydoes not affect an ability of eNB 102 to perform link adaptation forPUSCH transmissions that include those RBs as a respective UL CSI may beinterpolated from adjacent RBs where SRS is transmitted. For SRS BWsother than the maximum one, eNB 102 assigns to UE 114 a startingfrequency position for a P-SRS transmission by higher layer signaling.In an UL flexible TTI, SRS BW configuration c=0 920 (or another SRS BWconfiguration with larger maximum BW than SRS BW configuration 3) iseither default or indicated by additional system information which doesnot need to be interpreted by conventional UEs. A few RBs, 926 and 928,may again not be sounded by SRS but as previously mentioned this canhave a negligible impact. Moreover, as is subsequently discussed, somePUCCH transmissions may also be supported in RBs where SRS is nottransmitted. UE 114 is configured by higher layer signaling a SRStransmission BW with either m_(SRS,0) ⁰=96 RBs 932, or m_(SRS,1) ⁰=24RBs 934, or m_(SRS,2) ⁰=12 RBs 936, or m_(SRS,3) ⁰=4 RBs 938.

In a second approach for the SRS BW configuration in a reference cell,the BW in an UL flexible TTI can be divided into a first BW used for ULtransmissions and a second BW that is not used for UL transmissions. Ina neighboring cell using a different TDD UL-DL configuration than thereference cell, the BW in the DL flexible TTI can be divided into afirst BW that is not used for DL transmissions and into a second BW usedfor DL transmissions. In this manner, UL transmissions in the referencecell do not experience interference from DL transmissions in theneighboring cell (and the reverse). This first BW can be informed to UE114 by higher layer signaling or it can be specified in the operation ofthe communication system.

With the second approach, a P-SRS transmission can extend (partially orfully) over the first BW allocated to UL transmissions in order toprovide a respective UL CSI. A respective SRS BW configuration canfollow from the ones in TABLE 1 but a respective maximum SRS BW may notbe supported if it is larger than the first BW. The flexible TTIs forwhich UE 114 shall apply the above SRS transmission parameters can beindicated to UE 114 either by the DL signaling performing an adaptationof a TDD UL-DL configuration or it can be indicated, explicitly orimplicitly, by a DCI format scheduling a PDSCH or a PUSCH in theflexible TTI. For example, an explicit indication can be by including anInformation Element (IE) in the DCI formats for UEs configured foradaptation of a TDD UL-DL configuration indicating whether UE 114 shoulduse a first set of parameters or a second set of parameters for a PUSCHor a SRS transmission in a flexible TTI. An implicit indication can besimilar to the explicit one using a specific state of an existing IE.

Alternatively, with the second approach, the maximum SRS BW may still besupported by puncturing the last TTI symbol for PDSCH transmissions. Dueto the channel duality in TDD, this can allow eNB 102 to obtain somechannel information also for the DL.

FIG. 10 illustrates an example adaptation of SRS BW configuration in anUL flexible TTI when an UL BW is a fraction of an UL BW in an UL fixedTTI according to this disclosure. The embodiment of the SRS BWconfiguration shown in FIG. 10 is for illustration only. Otherembodiments could be used without departing from the scope of thepresent disclosure.

As shown in FIG. 10, a total UL BW consists of 100 RBs and is dividedinto a first UL BW 1010 consisting of 50 RBs and into a second BW 1015consisting of 50 RBs. UL transmissions from UE 114 occur only in thefirst BW. The SRS BW configuration can then be determined from TABLE 1and can support a maximum SRS transmission BW that is equal to orsmaller than the first UL BW. For example, SRS BW configuration c=7 canbe used with m_(SRS,0) ⁰=48 RBs 1022, or m_(SRS,1) ⁰=24 RBs 1024, orm_(SRS,2) ⁰=12 RBs 1026, or m_(SRS,3) ⁰=4 RBs 1028. A few RBs, 1030 mayagain not be sounded by SRS. A SRS BW configuration in an UL fixed TTIremains as in FIG. 9.

For the P-SRS transmission TTIs in case of UL flexible TTIs, UEs, suchas UE 114, can implicitly obtain this information from a respective onefor UL fixed TTIs or this information can also be included in higherlayer signaling configuring P-SRS transmissions in UL flexible TTIs. Thestarting UL flexible TTI can be the one immediately after the startingUL fixed TTI or can be the first UL flexible TTI in a frame and aperiodicity for P-SRS transmissions in an UL flexible TTIs can be sameor larger (as dictated by an availability of UL flexible TTIs per frame)as in UL fixed TTIs. For example, for TDD UL-DL configuration 2, if SIBsignaling indicates UL fixed TTI#2 as a starting P-SRS transmission ULTTI and a P-SRS transmission periodicity of 5 UL TTIs (implying thatTTI#7 also becomes an UL fixed TTI), a starting P-SRS transmission in anUL flexible TTI can be in UL TTI#3 and a periodicity of UL flexible TTIssupporting P-SRS transmissions can remain 5 UL TTIs and include ULflexible TTI#8. Therefore, a P-SRS transmission periodicity in a secondset of TTIs that includes UL flexible TTIs can be same as a P-SRStransmission periodicity in a first set of TTIs that includes UL fixedTTIs. For TDD UL-DL configuration 3, if SIB signaling indicates UL fixedTTI#2 as an UL TTI of starting P-SRS transmission and a P-SRStransmission periodicity of 10 UL TTIs, a starting P-SRS transmission inan UL flexible TTI can be in UL TTI#3 and a periodicity of UL flexibleTTIs supporting P-SRS transmissions can remain 10 UL TTIs.

For the multiplexing of HARQ-ACK signaling and P-SRS or for the numberof UpPTS symbols where P-SRS is transmitted, the choice signaled by aSIB for P-SRS transmissions in UL fixed TTIs also applies for ULflexible TTIs.

For P-SRS transmission parameters informed to UE 114 by higher layersignaling, such as RRC signaling, as previously mentioned separate RRCsignaling can be used for P-SRS transmissions in UL fixed TTIs and ULflexible TTIs. Therefore, a P-SRS transmission BW, frequency domainposition, transmission periodicity, hopping BW, cyclic shift, andfrequency comb for an UL flexible TTI can be provided to UE 114 byseparate higher layer signaling (in addition to the higher layersignaling providing these parameters for UL fixed TTIs). If anadaptation to any possible TDD UL-DL configuration is to be supported, aP-SRS transmission periodicity can be at least 10 TTIs.

Support of A-SRS Transmissions in an UL Flexible TTI

In certain embodiments, similar to P-SRS transmissions in UL flexibleTTIs, parameters for A-SRS transmissions in UL flexible TTIs can beseparately configured (than A-SRS transmissions in UL fixed TTIs). Forexample, for a A-SRS transmission triggered by a DCI format transmittedin a PDCCH scheduling a PUSCH, an A-SRS request field including one ortwo binary elements can indicate one set or three sets of A-SRStransmission parameters (assuming that one value of the A-SRS requestfield indicate no A-SRS transmission) that can include a transmissionBW, a frequency domain position, a cyclic shift, a frequency comb, and anumber of respective UE transmitter antennas if UE 114 has more than onetransmitter antenna. In general, an eNB can configure UE 114 with twosets of TTIs where typically a first set can contain fixed TTIs and asecond set can contain flexible TTIs.

FIG. 11 illustrates an example use of a first UE-specific higher layersignaling for P-SRS or A-SRS transmission parameters in an UL fixed TTIand of a second UE-specific higher layer signaling for P-SRS or A-SRStransmission parameters in an UL flexible TTI according to thisdisclosure. The embodiment shown in FIG. 11 is for illustration only.Other embodiments could be used without departing from the scope of thepresent disclosure.

As shown in FIG. 11, UE 114 is informed by first higher layer signalingof a first set of SRS transmission parameters 1110 for use in an ULfixed TTI 1120 and by second higher layer signaling of a second set ofP-SRS transmission parameters 1130 for use in an UL flexible fixed TTI1140. The SRS transmission parameters can be different for P-SRS and forA-SRS and can include one or more of a respective transmission BW, astarting frequency position, a cyclic shift of a ZC sequence, a spectralcomb, and a number of UE transmitter antennas (in case of multipleantennas, SRS transmission parameters other than ones for a firstantenna are implicitly derived from the ones for the first antenna).

Selection of UL TTI for an A-SRS Transmission

In certain embodiments, a determination of an UL TTI for an A-SRStransmission is considered when UE 114 receives an A-SRS request in aDCI format scheduling a PDSCH transmission to UE 114. An UL TTI for anA-SRS transmission triggered by a PDCCH in DL TTI n is conventionallydetermined as a first UL TTI satisfying n+k, k≥4 and(10·n_(f)+k_(SRS)−T_(offset,1))mod T_(SRS,1)=0 where k_(SRS) is a TTIindex within a frame n_(f), T_(offset,1) is an A-SRS TTI offset,T_(SRS,1) is an A-SRS periodicity. This conventional determination of anUL TTI for an A-SRS transmission can result to an A-SRS transmittedeither an UL fixed TTI or in an UL flexible TTI.

One option to resolve the above ambiguity is to re-interpret the A-SRStrigger in case of an adapted TDD UL-DL configuration as applying forA-SRS transmission in both an UL fixed TTI and an UL flexible TTI.Moreover, for UEs supporting adaptation of a TDD UL-DL configuration,the above constraint for k≥4 can be relaxed to k≥1.

If more refined control of whether an UL TTI of an A-SRS transmissionshould be in an UL fixed TTI or an UL flexible TTI is desired in orderto avoid unnecessary overhead compared to triggering A-SRS transmissionsfor both UL TTI types, eNB 102 can be restricted to transmitting arespective PDCCH in a predetermined DL TTI type associated with arespective UL TTI type. For example, triggering an A-SRS transmission inan UL flexible TTI or in an UL fixed TTI can be associated,respectively, with a DCI format scheduling a PDSCH that is transmittedin a DL flexible TTI or in a DL fixed TTI.

In general, a capability should be provided to eNB 102 to schedule PDSCHin any respective DL TTI type (fixed or flexible) and simultaneouslytrigger A-SRS transmission in any UL TTI type by decoupling an UL TTI ofan A-SRS transmission and a DL TTI of a respective PDCCH transmission.

A first option to provide the above flexibility to an eNB 102 schedulerfor operation in TDD systems is to extend the A-SRS request field by 1bit by including an UL TTI type A-SRS indicator field. This additionalbit can indicate whether an intended UL TTI for A-SRS transmission is afixed one or a flexible one. The determination is subject to theaforementioned conditions but if they indicate, for example, an UL fixedTTI while the UL TTI type A-SRS indicator field indicates an UL flexibleTTI, the A-SRS is transmitted in the first UL flexible TTI after the ULfixed TTI. Although this option can provide full flexibility to eNB 102scheduler, it effectively increases a size of an A-SRS request field.Moreover, although the description is with respect to a separate UL TTItype A-SRS indicator field, a same functionality is achieved byextending an A-SRS request field by 1 bit and having some of the statesof A-SRS transmission parameters include an UL fixed TTI and remainingones include an UL flexible TTI.

FIG. 12 illustrates an example use of an UL TTI type A-SRS indicatorfield according to this disclosure. The embodiment of the UL TTI typeA-SRS indicator field shown in FIG. 12 is for illustration only. Otherembodiments could be used without departing from the scope of thepresent disclosure.

As shown in FIG. 12, assuming an adapted TDD UL-DL configuration is TDDUL-DL configuration 1, UL TTI#2 1210 is an UL fixed TTI and UL TTI#31220 is an UL flexible TTI. If UE 114 detects a PDCCH in DL TTI#5 1230triggering an A-SRS transmission in UL TTI#2 subject to conventionalconditions while an UL TTI type A-SRS indicator field indicates an ULflexible TTI, the UE transmits the A-SRS in UL TTI#3.

A second option which trades off flexibility for additional overheadavoidance is to associate the DL TTI type of a PDCCH detectiontriggering an A-SRS transmission with the UL TTI type of the A-SRStransmission. If the DL TTI of a PDCCH transmission triggering an A-SRStransmission is fixed or flexible, the respective UL TTI for the A-SRStransmission is correspondingly fixed or flexible. If there are no ULflexible TTIs, then regardless of the DL TTI type for a PDCCH triggeringan A-SRS, the A-SRS is evidently transmitted in an UL fixed TTI. It isnoted that for any adaptation of a TDD UL-DL configuration, since DLTTIs of a conventional TDD UL-DL configuration cannot be changed to ULTTIs, there are always DL flexible TTIs.

A third option is to associate a value of an existing A-SRS requestfield with an UL TTI type for a respective A-SRS transmission. Forexample, for an A-SRS request field including 2 bits, a ‘01’ valueindicates a first conventional set of A-SRS transmission parameters andalso indicates A-SRS transmission in an UL fixed TTI while a ‘10’ valueindicates a second conventional set of A-SRS transmission parameters andalso indicates A-SRS transmission in an UL flexible TTI.

Periodic CSI Feedback for DL Fixed TTIs and for DL Flexible TTIs

In certain embodiments, P-CSI feedback for DL flexible TTIs isconsidered. In addition to providing an UL CSI, due to the DL/UL channelduality in a TDD system, a SRS transmission can also provide a channelestimate for the DL channel. However, as interference conditions aredifferent in an UL and a DL of a TDD system, a separate CSI feedback isrequired by UE 114 in order for eNB 102 to obtain information of SINRconditions experienced by DL signal transmission to UE 114 over the DLsystem BW. Due to difference in interference conditions in DL fixed TTIsand DL flexible TTIs, embodiments of the present disclosure considerthat UE 114 provides a first CSI for a DL fixed TTI and a second CSI fora DL flexible TTI. As a channel experienced by DL transmissions to UE114 is practically same in a DL fixed TTI and in a DL flexible TTI in asame frame, the above is functionally equivalent to UE 114 providing afirst Interference Measurement Report (IMR) for a DL fixed TTI and asecond IMR for a DL flexible TTI (assuming that the DL channel isknown). As the first CSI and the second CSI are obtained in differentTTIs, they can correspond to different ZP CSI-RS configurations (noadditional NZP CSI-RS configuration is needed). Therefore, aconventional restriction that UE 114 is not expected to receive CSI-IMresource configurations that are not all overlapping with one ZP CSI-RSresource configuration is no longer applicable. Moreover, consideringthat a DL fixed TTI and a DL flexible TTI can, in general, occurconsecutively in time (see TABLE 3), CSI-IM resources can be configuredin successive DL TTIs at least for DL flexible TTIs. Similar to theP-SRS transmission, UE 114 can assume that CSI-IM resources exist onlyin a first DL flexible TTI or can assume that they exist in eachflexible TTI in a configured set of flexible TTIs when the flexible TTIis indicated by the signaling adapting a TDD UL-DL configuration as a DLflexible TTI. A CSI from UE 114 can be provided to eNB 102 by a P-CSIreport in a PUCCH or an A-CSI report in a PUSCH.

A ZP CSI-RS in a DL flexible TTI can be supported similar to a P-SRS inan UL flexible TTI. CSI-IM resources and associated ZP CSI-RS parametersare configured to UE 114 by higher layer signaling, such as RRCsignaling, can include a ZP CSI-RS pattern index for ZP CSI-RS resources(see also REF 1), a ZP CSI-RS periodicity, and a DL TTI offset for a ZPCSI-RS in a frame (see also REF 3). eNB 102 can configure by separatehigher layer signaling the above ZP CSI-RS parameters in flexible TTIs.Alternatively, UE 114 can assume that a subset of the above ZP CSI-RSparameters is same in flexible TTIs as in fixed TTIs and remainingparameters, if any, can be provided by higher layer signaling (inadvance of adapting a TDD UL-DL configuration) or be implicitly derived.A TTI offset can correspond to a first DL flexible TTI after anadaptation of a TDD UL-DL configuration, or CSI-IM resources can existin flexible TTIs informed to UE 114 by higher layer signaling when theyare DL flexible TTIs, or CSI-IM resources can exist in every flexibleTTI when it is a DL flexible TTI. If UE 114 detects an adaptation of aTDD UL-DL configuration switching an UL TTI to a DL TTI and if UE 114determines (either explicitly by higher layer signaling or by animplicit predetermined rule as previously described) that the DL TTIincludes a ZP CSI-RS configuration and, therefore, associated CSI-IMresources, UE 114 can then perform respective interference measurements.Each respective interference measurement can be restricted in the DL TTIof a respective ZP CSI-RS transmission and may not include ZP CSI-RSresources in other DL TTIs. This is further discussed in a subsequentembodiment. Therefore, separate CSI-IM resources for interferencemeasurements can be associated with a DL fixed TTI and with a DLflexible TTI, each such CSI-IM resources need not belong to a same ZPCSI-RS resource configuration, and a conventional restriction that UE114 is not expected to receive CSI-IM resource configurations that arenot all completely overlapping with one ZP CSI-RS resource configurationdoes not apply.

Similar to the second approach of the first embodiment of the presentdisclosure for the transmission of P-SRS in an UL flexible TTI, a BW canbe divided in a first BW and in a second BW and UE 114 can assume thatDL transmissions in a DL flexible TTI can occur only in the second BW.In that case, UE 114 can perform measurements based on a CSI-RS in suchflexible TTI only over the second BW. UE 114 can be informed of a firstBW (and therefore of a second BW) by eNB 102 through higher layersignaling.

A first option for multiplexing a P-CSI report for a measurement in a DLfixed TTI with a P-CSI report for a measurement in a DL flexible TTI istime domain multiplexing. Then, eNB 102 can provide separate higherlayer signaling to UE 114 informing of P-CSI transmission parameters forreporting measurements obtained in DL fixed TTIs and in DL flexibleTTIs. Such parameters include an UL TTI and a periodicity for a P-CSItransmission, contents of a P-CSI transmission (such as only CQI or bothCQI and PMI), and parameters for determining a PUCCH resource for aP-CSI transmission for a respective PUCCH format. If the twoaforementioned P-CSI report types need to be transmitted in a same ULTTI then, if UE 114 is not capable of simultaneously transmitting morethan one PUCCH, UE 114 shall prioritize for transmission one P-CSIreport and suspend transmission of the other P-CSI report. As eNB 102needs to know the relevance of a P-CSI report, a rule needs to apply forwhich P-CSI report is transmitted in case a transmission of both P-CSIreport types coincides in a same UL TTI. Therefore, after UE 114prioritizes a P-CSI transmission according to the lower CSI processindex (if multiple such processes exist) and according to a DL cellindex (if multiple such DL cells exist), as it was previously described(see also REF 3), embodiments of the present disclosure consider that UE114 is informed for a P-CSI report prioritization either by a 1-bithigher layer signaling from eNB 102, or by an implicit rule according toa P-CSI report index (0 or 1), or by a fixed rule in the operation ofthe communication system such as always prioritizing transmission forthe P-CSI report corresponding to a DL flexible TTI (or to a DL fixedTTI), or for suspending the P-CSI report having a more recenttransmission in a previous UL TTI.

The first option decouples P-CSI reporting corresponding to DL fixedTTIs and DL flexible TTIs by using TDM. However, an availability of ULfixed TTIs per frame can be low, such as one UL fixed TTI per frame forTDD UL-DL configuration 5, thereby necessitating long periodicities foreach P-CSI report in order to avoid a P-CSI report corresponding to a DLfixed TTI having to be transmitted in a same UL TTI as a P-CSI reportcorresponding to a DL flexible TTI. Unless a channel experienced by UE114 is practically stationary, long P-CSI reporting periodicities can bedetrimental to DL system throughput.

A second option for multiplexing a P-CSI report for a measurement in aDL fixed TTI with a P-CSI report for a measurement in a DL flexible TTIis by joint coding in a same PUCCH. This can be either a default choiceor indicated to UE 114 by higher layer signaling. Even though a PUCCHformat may not be able to support a maximum payload for both P-CSIreport types resulting from reporting both CQI and PMI, such maximumpayloads can be avoided if eNB 102 obtains a PMI from a SRS transmittedfrom UE 114 and P-CSI reports convey only CQI which may further berestricted to be only for transmission rank 1 in order to further reduceits payload. Additionally, a first UE 114 reporting both P-CSI types canuse a different transmission format than a second conventional UE 115reporting on a first P-CSI type. For example, the first UE 114 can use aformat supporting higher P-CSI payloads and referred to as PUCCH format3, while the second UE 115 can use a format supporting lower P-CSIpayloads and referred to as PUCCH format 2. Therefore, a conventional UEalways transmits a single P-CSI using a PUCCH format 2 while UE 114supporting adaptation of a TDD UL-DL configuration can be configured byeNB 102 whether to transmit both a P-CSI report for a measurement in aDL fixed TTI and a P-CSI report for a measurement in a DL flexible TTIin a same PUCCH format 2 or in a same PUCCH format 3.

Similar to P-SRS transmission, a P-CSI can be transmitted in an ULflexible TTI and UE 114 can be provided by higher layer signaling fromeNB 102 a second set of parameters for P-CSI transmissions in an ULflexible TTI (in addition to the first set of parameters for P-CSItransmissions in an UL fixed TTI). Unlike conventional P-CSI and P-SRStransmissions that are not allowed to occur simultaneously as theirtransmissions can be arranged by eNB 102 to occur in different UL TTIs,such arrangement may not be possible for a P-CSI report for ameasurement in a DL flexible TTI as an adaptation rate of an TDD UL-DLconfiguration may not be long enough to avoid such simultaneoustransmissions especially when a number of UL TTIs per frame is small.Therefore, the invention further considers that, unlike conventionalUEs, UEs supporting adaptation of a TDD UL-DL configuration can alsosupport simultaneous P-CSI and P-SRS transmissions by puncturing P-CSItransmission in a last TTI symbol of a respective PUCCH in order totransmit P-SRS.

Aperiodic CSI Feedback for DL Fixed TTIs and for DL Flexible TTIs

In certain embodiments, A-CSI feedback for DL flexible TTIs isconsidered. For A-CSI reporting by UE 114 supporting adaptation of a TDDUL-DL configuration on a fast time scale, given the existence ofdifferent A-CSI report types computed by respective measurements in DLfixed TTIs and in DL flexible TTIs, UE 114 behavior needs to be furtherdefined when it detects a PDCCH conveying a DCI format including anA-CSI request field indicating that UE 114 should include an A-CSIreport with its scheduled PUSCH transmission.

In a first option, embodiments of the present disclosure consider thatif a CSI request field includes 1 bit, a value of binary ‘0’ indicatesthat UE 114 shall not multiplex any A-CSI report in the PUSCHtransmission while a value of ‘1’ indicates that UE 114 shall multiplexboth an A-CSI report for a measurement in a DL fixed TTI and an A-CSIreport for a measurement in a DL flexible TTI.

If the DCI format scheduling a PUSCH transmission from UE 114 has anA-CSI request field that includes 2 bits, this can provide additionalflexibility in selecting an A-CSI report type for multiplexing in aPUSCH transmission and provide to eNB 102 means for controlling arespective A-CSI overhead as needed. TABLE 4 provides an indicativemapping of an A-CSI request field to triggering of A-CSI report types.

TABLE 4 Mapping of A-CSI Request Field Values to A-CSI Report Types.Value of CSI request field Description ‘00’ No A-CSI report is triggered‘01’ A-CSI report is triggered for a CSI measurement associated with DLfixed TTIs ‘10’ A-CSI report is triggered for a CSI measurementassociated with DL flexible TTIs ‘11’ A-CSI report is triggered both fora CSI measurement associated with DL fixed TTIs and for a CSImeasurement associated with DL flexible TTIs

A support for indicating an A-CSI type can further be extended in caseDL Carrier Aggregation (CA) or DL Coordinated Multi-Point (COMP)transmission is supported in conjunction with an adaptive TDD UL-DLconfiguration. For example, in case of also supporting DL CA, an A-CSIrequest field may include 3 bits with an indicative mapping as in TABLE5.

TABLE 5 Mapping of A-CSI Request Field Values to A-CSI Report Types.Value of CSI request field Description ‘000’ No A-CSI report istriggered ‘001’ A-CSI report is triggered for a CSI measurementassociated with DL fixed TTIs and for serving cell c ‘010’ A-CSI reportis triggered for a CSI measurement associated with DL flexible TTIs andfor serving cell c ‘011’ A-CSI report is triggered for a CSI measurementassociated with DL fixed TTIs and for a 1^(st) set of serving cellsconfigured by higher layers ‘100’ A-CSI report is triggered for a CSImeasurement associated with DL flexible TTIs and for a 1^(st) set ofserving cells configured by higher layers ‘101’ A-CSI report istriggered for a CSI measurement associated with DL fixed TTIs and for a2^(nd) set of serving cells configured by higher layers ‘110’ A-CSIreport is triggered for a CSI measurement associated with DL flexibleTTIs and for a 2^(nd) set of serving cells configured by higher layers‘111’ Reserved

A support for indicating an A-CSI type can be further extended toindicate a respective measurement report for a specific DL flexible TTI.A same correspondence to a specific DL flexible TTI can be defined for aP-CSI report. The reason for distinguishing among DL flexible TTIs isbecause a respective interference can be different for different DLflexible TTIs. Alternatively, UE 114 can determine how to perform theCSI measurements as described in a subsequent embodiment.

FIG. 13 illustrates an example for an existence of differentinterference characteristics in different flexible TTIs according tothis disclosure. The embodiment of the TTIs shown in FIG. 13 is forillustration only. Other embodiments could be used without departingfrom the scope of the present disclosure.

As shown in FIG. 13, TDD UL-DL configuration 1 is used in referencecell#1 1310, TDD UL-DL configuration 2 is used in interfering cell#21320, and TDD UL-DL configuration 3 is used in interfering cell#3 1330.In DL TTI#0 (or DL TTI#0, DL TTI#5, DL TTI#6, and DL TTI#9) in cell#11340, cell#2 1350, and cell#3 1360, an interference experienced by DLtransmissions is statistically same. In TTI#3, an interference in cell#21352 is from UL transmissions both in cell#1 1342 and in cell#3 1362.Therefore, in TTI#3, PDSCH transmissions to UE 114 in cell#2 that islocated towards cell#1 or cell#3 experiences interference from ULtransmissions. In TTI#4, an interference in cell#2 1354 is from DLtransmissions in cell#1 1344 but from UL transmissions in cell#3 1364.Therefore, in TTI#4, a PDSCH transmission to UE 114 in cell#2 that islocated towards cell#1 experiences interference from DL transmissionsand a PDSCH transmission to UE 114 in cell#2 that is located towardscell#3 experiences interference from UL transmissions. Finally, inTTI#8, an interference in cell#2 1356 is from UL transmissions in cell#11346 but from DL transmissions in cell#3 1366. Therefore, in TTI#8, aPDSCH transmission to UE 114 in cell#2 that is located towards cell#1experiences interference from UL transmissions and a PDSCH transmissionto UE 114 in cell#2 that is located towards cell#3 experiencesinterference from DL transmissions. In conclusion, not only there existsinterference variation between the two DL TTI types (DL fixed TTIs andDL flexible TTIs) but also there exists interference variation indifferent DL flexible TTIs.

In one approach to address such interference dependence on an index of aDL flexible TTI, respective P-CSI and A-CSI reporting processes can besupported that are based on a measurement using CSI-IM resources onlyfor the corresponding DL TTI. For P-CSI, respective reports can besupported based on previously described methods for supporting P-CSI forDL fixed TTIs and for a DL flexible TTI.

For A-CSI reporting, same options exist as described for A-SRS reportingwhen triggered by a DCI format scheduling a PDSCH. Therefore, in a firstoption, if an A-CSI report is triggered, all A-CSI reports forrespective DL flexible TTIs can be included in a same PUSCH. In a secondoption, if the DL TTI of a PDCCH transmission triggering an A-CSI reportis fixed or flexible, the respective DL TTI for the A-CSI report iscorrespondingly fixed or flexible. In a third option, the A-CSI requestfield can be further expanded to provide an index to specific DL TTIsfor which respective A-CSI reports are to be included in a PUSCH.

In addition, for A-CSI reporting in a PUSCH transmission from UE 114 toeNB 102, an additional option (relative to the previous ones that arealso in principle applicable for triggering A-SRS transmission from a UEto an eNB) can be based on a Cyclic Shift (CS) and Orthogonal CoveringCode (OCC) field (CS-OCC field) that exists in a DCI format schedulingthe PUSCH and triggering the A-CSI reporting (see also REF 2). TheCS-OCC field informs UE 114 of a CS and an OCC to apply to the DMRStransmission in the PUSCH, in order to facilitate spatial multiplexingof PUSCH transmissions from different UEs, and of a resource for anacknowledgement signal transmission from eNB 102 in response to thePUSCH reception (see also REF 1 and REF 3). The CS-OCC field is assumedto include 3 bits. Communication systems operating with an adaptive TDDUL-DL configuration intend to adapt to fast variations of a totaltraffic in a cell. Statistically, the smaller a number of UEs havingactive communication in a cell, the larger the variations in a totaltraffic in the cell. Therefore, operation with an adaptive TDD UL-DLconfiguration is associated with a typically small number of UEs havingactive communication in a cell and a CS-OCC field can provide theintended functionalities with less than 3 bits, such as 2 bits. Then,the additional bit can be used to supplement a CSI request field thatincludes 1 bit or 2 bits and respectively provide a CSI request fieldthat includes 2 bits or 3 bits as it was previously described. Forexample, the Most Significant Bit (MSB) of a CS-OCC field can supplementa CSI request field as the MSB of the CSI request field. For example, 4CS-OCC states, of the 8 CS-OCC states addressable by a 3-bit CS-OCCfield, can be remapped to a 2-bit CS-OCC field.

Using SRS for Link Adaptation of DL Transmissions

In this embodiment, eNB 102 can use a reception of a SRS transmittedfrom a UE to perform link adaptation for DL transmissions to UE 114. Ina TDD system, a channel medium is same for DL transmissions and for ULtransmissions as a same carrier frequency is used. In a conventional TDDsystem, where interference to DL transmissions in a cell is from DLtransmissions in neighboring cells, as a same TDD UL-DL configuration istypically assumed, UE 114 needs to provide CSI feedback to eNB 102 asSRS transmissions can provide information for the channel medium butcannot provide information for interference experienced by DLtransmissions to UE 114 from eNB 102 as this interference is typicallysignificantly different that the interference experienced by ULtransmissions from UE 114 to eNB 102.

For a TDD system operating with an adaptive TDD UL-DL configuration, twosets of UL TTIs exist where in a first set of UL TTIs UL interference isdominant and in a second set of UL TTIs DL interference is dominant.Moreover, two sets of DL TTIs exist where in a first set of DL TTIs DLinterference is dominant and in a second set of DL TTIs UL interferenceis dominant.

Therefore, when the previous two sets of TTIs exist, a SRS transmissionin the first set of UL TTIs can be used for DL link adaptation for thesecond set of DL TTIs as, especially since UE 114 typically experiencesone dominant interferer, the first set of UL TTIs and the second set ofDL TTIs experience the same UL interference. Similar, a SRS transmissionin the second set of UL TTIs can be used for DL link adaptation for thefirst set of DL TTIs as, for one dominant interferer, the second set ofUL TTIs and the first set of UL TTIs experience the same DLinterference.

Using SRS transmissions to obtain a CSI for DL transmissions, as it waspreviously described, can be advantageous to a system operation overrelying on CSI feedback from a UE for several reasons that include:

-   -   a) SRS transmissions are not subject to quantization errors;    -   b) SRS transmissions are not subject to detection (decoding)        errors;    -   c) SRS transmissions can provide CSI over substantially an        entire bandwidth while CSI feedback from UE 114 provides only        average information over the entire bandwidth or information for        only a few sub-bands of the entire bandwidth; and    -   d) SRS transmissions typically require significantly less UL        overhead than CSI transmissions.

FIG. 14 illustrates an example determination by eNB 102 of a DL CSI in afirst set of DL TTIs using a SRS transmission from UE 114 in a secondset of UL TTIs according to this disclosure. While the flow chartdepicts a series of sequential steps, unless explicitly stated, noinference should be drawn from that sequence regarding specific order ofperformance, performance of steps or portions thereof serially ratherthan concurrently or in an overlapping manner, or performance of thesteps depicted exclusively without the occurrence of intervening orintermediate steps. The process depicted in the example depicted isimplemented by a transmitter chain in, for example, a mobile station.

As shown in FIG. 14, UE 114 transmits SRS in an UL TTI from a first setof UL TTIs where UL transmissions from UE 114 experience a dominant ULinterference in operation 1410. In operation 1420, eNB 102 receives theSRS transmission from UE 114 and, based on the received SRS, eNB 102computes a CSI for a second set of DL TTIs where DL transmissions to UE114 experience a dominant UL interference in operation 1425.Alternatively, UE 114 transmits SRS in an UL TTI from a second set of ULTTIs where UL transmissions from UE 114 experience a dominant DLinterference in operation 1430. In operation 1440, eNB 102 receives theSRS transmission from UE 114 and, based on the received SRS, eNB 102computes a CSI for a first set of DL TTIs where DL transmissions to UE114 experience a dominant DL interference in operation 1445.

FIG. 15 illustrates an example eNB receiver for estimating a DL CSI in aTTI set based on a SRS transmission from a UE according to thisdisclosure. The embodiment of the receiver 1500 shown in FIG. 15 is forillustration only. Other embodiments could be used without departingfrom the scope of the present disclosure. In certain embodiments, theeNB receiver 1500 shown in FIG. 15 is implemented in eNB 102.

As shown in FIG. 15, eNB 102 receives a SRS transmitted from UE 114 inan UL TTI from a first set of UL TTIs where the SRS experiences ULinterference 1510. After filtering 1520 and CP removal 1525, an outputis provided to a serial-to-parallel (S/P) converter 1530 andsubsequently an IFFT is performed 1540 and a reception bandwidth controlunit 1550 selects REs of SRS reception 1555. Element-wise multiplication1560 with a Zadoff-Chu based sequence 1565 UE 115 used to transmit theSRS follows and an output is provided to an IDFT 1570 and, afterrestoring a cyclic shift applied to the SRS transmission 1585, a DFT isperformed 1580 and a CSI estimate for DL signal transmissions in a DLTTI of a second set of DL TTIs where DL signal transmissions experienceUL interference is obtained 1590. A same receiver structure can be usedto obtain a CSI estimate for DL signal transmissions in a DL TTI of afirst set of DL TTIs where DL signal transmissions experience DLinterference based on a reception of a SRS transmitted from UE 114 in anUL TTI from a second set of UL TTIs where the SRS experiences DLinterference.

Additionally, eNB 102 can use SRS transmissions in conjunction with CSIfeedback from UE 114 in order to compute a DL CSI for a first set of DLTTIs or for a second set of DL TTIs. For example, eNB 102 can use a SRStransmission from UE 114 in a second set of UL TTIs, as it waspreviously described, in conjunction with a CSI feedback from UE 114 fora first set of DL TTIs to compute a CSI for the first set of DL TTIs.Similar, eNB 102 can use a SRS transmission from UE 114 in a first setof UL TTIs, as it was previously described, in conjunction with a CSIfeedback from UE 114 for a second set of DL TTIs to compute a CSI forthe second set of DL TTIs.

UE CSI Measurements

In certain embodiments, a measurement procedure is described for UE 114to report CSI for a first set of DL TTIs, such as a set including DLTTIs where DL transmissions from eNB 102 to UE 114 experiences dominantDL interference, and for a second set of DL TTIs, such as a setincluding DL TTIs where UE 114 experiences dominant UL interference.

CSI measurements from UE 114 in a first DL TTI set and in a second DLTTI set can be based either on a CRS or on a CSI-RS, for exampledepending of a transmission mode UE 114 is configured for PDSCHreceptions. A CSI measurement can be derived from a measurement ofanother quantity, such as a SINR, and can also consider UE 114 receivercapability.

As a first set of DL TTIs and a second set of DL TTIs are configured toUE 114 by higher layer signaling, such as RRC signaling, and as theinterference type (DL or UL) can vary on a faster time scale due to arespective adaptation of a TDD UL-DL configuration, the first DL TTI setor the second DL TTI set can include DL TTIs where UE 114 experienceseither DL dominant interference or UL dominant interference. Forexample, the first DL TTI set can include only TTIs that are DLsubframes in an adapted TDD UL-DL configuration and are UL TTIs in aconventional TDD UL-DL configuration and the second DL TTI set caninclude TTIs that are DL TTIs (or special TTIs) in both an adapted TDDUL-DL configuration and a conventional TDD UL-DL configuration. In thisexample, a DL signal transmission in a DL TTI from the first set of DLTTIs can experience either UL-dominant or DL-dominant interference whilea DL signal transmission in a DL TTI from the second set of DL TTIs cantypically experience only DL-dominant interference when interferingcells are assumed to use a same conventional configuration but can usedifferent respective adapted TDD UL-DL configurations.

In general, for proper DL scheduling, it is desirable for UE 114 toavoid measuring a same CSI over DL TTIs that experience both DL-dominantinterference and UL-dominant interference. Instead, it is desirable forUE 114 to provide a first CSI that captures only DL-dominantinterference and a second CSI that captures only UL-dominantinterference to DL signaling transmissions from eNB 102, particularly ifeNB 102 knows the DL TTIs where UE 114 experiences each dominantinterference type (DL or UL).

For example, referring to FIG. 13, UE 114 located in Cell#2 (that usesTDD UL-DL configuration 2) and experiences interference from Cell#3(that uses TDD UL-DL configuration 3), can have as TTI#3, TTI#4, andTTI#8 configured by eNB 102 to be in a same set of TTIs for CSIreporting by UE 114. A DL transmission to UE 114 in TTI#3 or TTI#4experiences UL-dominant interference while a DL transmission to UE 114in TTI#8 experiences DL-dominant interference. As a consequence, a SINRmeasurement (based on a CRS or on a CSI-RS) by UE 114 in TTI#3 or TTI#4is likely to be larger than a SINR measurement by UE 114 in TTI#8 as ULinterference is typically smaller than DL interference. Therefore, ifeNB 102 knows the type of dominant interference (DL or UL) UE 114experiences in a TTI, it is beneficial for UE 114 to only includemeasurements in TTI#3 or TTI#4 (and not include measurements in TTI#8)in deriving a CSI for a respective set of TTIs. Otherwise, if forexample UE 114 derives a CSI based on filtered measurements, such as anaverage of measurements, in TTI#3, TTI#4, and TTI#8, the CSI is likelyto be pessimistic for TTI#3 and TTI#4. Then, although eNB 102 can beaware of this pessimistic CSI report for TTI#3 and TTI#4, it cannotdetermine a proper CSI for link adaptation of a DL transmission to UE114 in TTI#3 or TTI#4. Conversely, if TTI#0, TTI#1, TTI#5, TTI#6, andTTI#9 are in a same set of TTIs, a SINR measurement can be expected tobe similar as UE 114 experiences DL-dominant interference in all theseTTIs and UE 114 can derive a CSI based on filtered measurements in allTTIs in the set of TTIs or based on filtered measurements in any TTIs inthe set of TTIs.

For UE 114 to separate a determination of CSI corresponding to TTIs withDL-dominant interference from a determination of CSI corresponding toTTIs with UL-dominant interference, embodiments of the presentdisclosure consider that UE 114 uses a threshold for determining whetheror not to include a measurement it obtains in a DL TTI in a filteredaverage of measurements it computes for deriving a first CSI or a secondCSI. For example, for deriving a first CSI that captures DL-dominantinterference, UE 114 can include in a filtered average only measurementsthat are below a first threshold while for computing a second CSI thatcaptures UL-dominant interference, UE 114 can include in a filteredaverage only measurements that are at or above a second threshold. Forexample, the first threshold and the second threshold can be same. Forexample, the first threshold and the second threshold can be computed byUE 114 as an average of a first number of smallest measurement valuesand a first number of largest measurement values over respective DLTTIs.

FIG. 16 illustrates an example for a UE to determine a first CSI from afirst set of DL TTIs or to determine a second CSI from a second set ofDL TTIs according to this disclosure. The embodiment of the TTIs shownin FIG. 16 is for illustration only. Other embodiments could be usedwithout departing from the scope of the present disclosure.

As shown in FIG. 16, UE 114 operates with TDD UL-DL configuration 21610. UE 114 is configured a first set of TTIs (subframes), thatincludes TTI#0 1620, TTI#1 1622, TTI#5 1624, TTI#6 1626, and TTI#9 1628,for measurements corresponding to a first CSI. UE 114 is also configureda second set of TTIs, that includes TTI#3 1630, TTI#4 1632, TTI#8 1634,for measurements corresponding to a second CSI. TTI#7 can also beincluded in one of the sets, such as the second set, but for TDD UL-DLconfiguration 2 it is an UL TTI and therefore cannot be used for CSImeasurements. The measurements can be, for example, SINR ones based onCRS (in DL TTIs that include CRS). UE 114 compares a measurement in arespective DL TTI in the first set of TTIs to a threshold 1640. If themeasurement is above the threshold, the DL TTI is not considered for thecomputation of the first CSI; otherwise, the DL TTI can be consideredfor the computation of the first CSI. UE 114 also compares a measurementin a respective DL TTI in the second set of TTIs to the threshold 1640.If the measurement is below the threshold, the DL TTI is not consideredfor the computation of the second CSI; otherwise, the DL TTI can beconsidered for the computation of the second CSI. Therefore, based onthe measurements in TTI#0 1650, TTI#1 1652, TTI#5 1654, TTI#6 1656, andTTI#9 1658, UE 114 can consider these first four TTIs for a computationof the first CSI the TTI but does not consider TTI#9. Based on themeasurements in TTI#3 1660, TTI#4 1662, and TTI#8 1664, UE 114 canconsider these first two TTIs for a computation of the second CSI theTTI but does not consider TTI#8. In one option, TTI#9 and TTI#8 can bediscarded for any CSI computation. In another option, TTI#9 can beconsidered for the second CSI computation while TTI#8 can be consideredfor the first CSI computation despite being associated with the first DLTTI set and the second DL TTI set, respectively.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for a user equipment (UE) to transmit achannel state information (CSI) report, the method comprising: receivinginformation for first and second sets of time resources over a timeperiod, wherein at least one time resource from the second set of timeresources is associated with a first transmission direction in a firsttime period and with a second transmission direction in a second timeperiod; receiving respective first and second channel stateinformation-interference measurement (CSI-IM) resource configurationsfor a same CSI-process for the first and second sets of time resources;performing first and second interference measurements based onrespective first and second CSI-IM resource configurations; andtransmitting a CSI report based on the first or second interferencemeasurement.
 2. The method of claim 1, wherein the CSI process includesa single non-zero power reference signal (CSI-RS) configuration.
 3. Themethod of claim 1, wherein the transmitting comprises: when the UE isconfigured for simultaneous transmission of both a CSI report for thefirst set of time resources and a CSI report for the second set of timeresources for a same serving cell, prioritizing transmission of only aCSI report for one of the first set of time resources or the second setof time resources that is associated with a smaller index.
 4. The methodof claim 1, further comprising: receiving a downlink control information(DCI) including a CSI request field, wherein the CSI request field hastwo bits that trigger at least one of a CSI report for the first set oftime resources and a CSI report for the second set of time resources. 5.The method of claim 1, further comprising: receiving a downlink controlinformation (DCI) indicating a transmission direction for a timeresource in the second set of time resources; and performing aninterference measurement in the time resource in the second set of timeresources only when the DCI indicates a downlink direction for the timeresource in the second set of time resources.
 6. A user equipment (UE),comprising: a transceiver; and a processor coupled to the transceiver,wherein the processor is configured to: receive information for firstand second sets of time resources over a time period, wherein at leastone time resource from the second set of time resources is associatedwith a first transmission direction in a first time period and with asecond transmission direction in a second time period; receiverespective first and second channel state information-interferencemeasurement (CSI-IM) resource configurations for a same CSI-process forthe first and second sets of time resources; perform a firstinterference measurement based on the first CSI-IM resourceconfiguration and a second interference measurement based on the secondCSI-IM resource configuration; and transmit a CSI report based on thefirst interference measurement or on the second interferencemeasurement.
 7. The UE of claim 6, wherein the CSI process includes asingle non-zero power reference signal (CSI-RS) configuration.
 8. The UEof claim 6, wherein the processor is configured to transmit the CSI by:when the UE is configured for simultaneous transmission of both a CSIreport for the first set of time resources and a CSI report for thesecond set of time resources for a same serving cell, prioritizingtransmission of only a CSI report for one of the first set of timeresources or the second set of time resources that is associated with asmaller index.
 9. The UE of claim 6, wherein the processor is furtherconfigured to: receive a downlink control information (DCI) including aCSI request field, wherein the CSI request field has two bits thattrigger at least one of a CSI report for the first set of time resourcesand a CSI report for the second set of time resources.
 10. The UE ofclaim 6, wherein the processor is further configured to: receive adownlink control information (DCI) indicating a transmission directionfor a time resource in the second set of time resources; and perform aninterference measurement in the time resource in the second set of timeresources only when the DCI indicates a downlink direction for the timeresource in the second set of time resources.
 11. A method for a basestation to receive a channel state information (CSI) report, the methodcomprising: transmitting information for first and second sets of timeresources over a time period, wherein at least one time resource fromthe second set of time resources is associated with a first transmissiondirection in a first time period and with a second transmissiondirection in a second time period; transmitting respective first andsecond channel state information-interference measurement (CSI-IM)resource configurations for a same CSI-process for the first and secondsets of time resources; and receiving a CSI report based on aninterference measurement using the first CSI-IM resource configurationor on a second interference measurement using the second CSI-IM resourceconfiguration.
 12. The method of claim 11, wherein the CSI processincludes a single non-zero power reference signal (CSI-RS)configuration.
 13. The method of claim 11, wherein the receivingcomprises: when the base station is configured for simultaneouslyreceiving both a CSI report for the first set of time resources and aCSI report for the second set of time resources for a same serving cell,receiving a CSI report only for one of the first or second sets of timeresources that is associated with a smaller index.
 14. The method ofclaim 11, further comprising: transmitting a downlink controlinformation (DCI) including a CSI request field, wherein the CSI requestfield has two bits that trigger at least one of a CSI report for thefirst set of time resources and a CSI report for the second set of timeresources.
 15. The method of claim 11, further comprising transmitting adownlink control information (DCI) indicating a transmission directionfor a time resource in the second set of time resources.
 16. A basestation, comprising: a transceiver; and a processor coupled to thetransceiver, wherein the processor is configured to: transmitinformation for first and second sets of time resources over a timeperiod, wherein at least one time resource from the second set of timeresources is associated with a first transmission direction in a firsttime period and with a second transmission direction in a second timeperiod; transmit respective first and second channel stateinformation-interference measurement (CSI-IM) resource configurationsfor a same CSI-process for the first and second sets of time resources;and receive a CSI report based on a first interference measurement usingthe first CSI-IM resource configuration or on a second interferencemeasurement using the second CSI-IM resource configuration.
 17. The basestation of claim 16, wherein the CSI process includes a single non-zeropower reference signal (CSI-RS) configuration.
 18. The base station ofclaim 16, wherein the processor is configured to receive the CSI by:when the base station is configured for simultaneously receiving both aCSI report for the first set of time resources and a CSI report for thesecond set of time resource for a same serving cell, receiving a CSIreport only for one of the first or second set of time resources that isassociated with a smaller index.
 19. The base station of claim 16,wherein the processor is further configured to: transmit a downlinkcontrol information (DCI) including a CSI request field, wherein the CSIrequest field has two bits that trigger at least one of a CSI report forthe first set of time resources and a CSI report for the second set oftime resources.
 20. The base station of claim 16, wherein the processoris further configured to transmit a downlink control information (DCI)indicating a transmission direction for a time resource in the secondset of time resources.